The invention relates to a line arrangement for transmitting volume flows of fluids, having a port which is assigned to a pump, a port which is assigned to an actuator and a connecting line which connects the pump to the actuator.
In such hydraulic lines, pressure pulsations may arise which excite resonances in the lines which may not only be the cause of disrupting noises but also of loosening of screwed connections and/or of wear.
In order to avoid these difficulties it is known to connect one or more pressure convectors to the lines through which fluids flow and which are configured in their volume and in their pilot pressure in such a way that they as far as possible damp the pressure fluctuations which occur. A disadvantage with these pressure accumulators is, however, that they have a large volume and are thus heavy, which leads to problems in many areas of application of line arrangements owing to the poor adaptability. In addition, these known solutions are relatively expensive and difficult to configure or adjust to the respective application case.
Furthermore, in order to avoid pressure pulsations in lines, it is known, for example, from DE 35 10 267 A1, to provide a feed hose—i.e. a hose through which there is a flow and which is arranged between the pump and actuator—which is provided with an outer flexible hose part and an inner flexible hose part which is arranged coaxially in the outer hose part and extends only over part of the outer hose part. The inner hose part is connected by one of its ends to a connecting element to the outer hose part, and forms with the outer hose part an elongated, annular space. As the inner hose part does not extend over the entire length of the outer hose part, an empty chamber is produced adjacent to the elongated annular space. This is a region in which the fluid is surrounded only by the outer hose part. In this fluid arrangement, the fluid firstly flows through the inner hose part before it flows into the empty chamber. The inner hose part is therefore oriented with its free end in the direction of the actuator, in other words in the flow direction.
The known damping element acts as follows: in the described hose arrangement, pressure pulsations run firstly into the empty chamber via the inner hose part. Some of the migrating pulsation waves will propagate in the downstream direction in the empty chamber while other pulsation waves will propagate in the upstream direction in the elongated annular space between the inner and outer hose parts. The waves which are directed upstream are deflected at the inner end wall of the connecting element and migrate downstream again in the annular cavity and are superimposed on the migrating pulsation waves which emerge from the inner hose part. In this superimposition process, the waves are partially superimposed one on the other in antiphase, resulting in a damping effect.
In some hydraulic systems, in particular in piston pumps, the damping effect of the described line arrangement is not sufficient to damp adequately the high emission of pulsations, and thus the high emission of noise of the pump.
Against this background, the object of the present invention is to provide a line arrangement for transmitting volume flows of the above mentioned type in which the damping effect is amplified.
This object is achieved with a line arrangement for transmitting volume flows of fluids, having a port which is assigned to a pump, a port which is assigned to an actuator, and a connecting line which connects the pump to the actuator, wherein at least one line through which there is not a flow and which is at least partially composed of an elastic hose branches off from the connecting line. This object is also achieved by providing a line arrangement for transmitting volume flows of fluids, having a port which is assigned to a pump, a port which is assigned to an actuator, and a connecting line which connects the pump to the actuator, wherein at least one line which runs in parallel with the connecting line and which is composed at least partially of an elastic hose is provided.
Accordingly, the solution according to the invention is defined in that at least one line through which there is not a flow and which branches off from a connecting line between pump and load is provided in the line arrangement. This line through which there is not a flow is composed at least partially of an elastic hose and is closed off at its end facing away from the branch. Owing to the resilience of the hose wall at increased pressures, the line through which there is not a flow can replace a relatively large volume and as a result compensate pressure pulsations. If such a resilient hose through which there is not a flow is connected to a hose arrangement of this generic type, the damping effect which is described acts on the entire line arrangement. The arrangement according to the invention brings about considerable damping of the pulsations, which is manifest in particular by drastically lower noise emissions of the pump.
The elastic hose can extend over the entire length of the line through which there is not a flow. However, it can extend over only part of this line, the other part being composed, for example, of a metal tube.
The described object is also achieved by a line arrangement of the generic type in which at least one line which runs in parallel with the connecting line and which is composed of an elastic hose is provided. In this context, a line which is guided in parallel is to be understood as a line which branches off from the connecting line at one location and joins it again at another location downstream on the connecting line. In this exemplary embodiment, the fluid which is fed through the line arrangement is therefore conducted in parallel through both lines. Owing to the resilience of the hose wall, the line which is guided in parallel also has the effect of compensating pulsations in this case, which has a positive effect on the noise emissions of the line arrangement.
The line which is guided in parallel can be composed completely or only partially of an elastic hose.
According to one embodiment, the lines through which there is not a flow and which are guided in parallel branch off directly at the port of the connecting line which is assigned to the pump. In this case, particularly good degrees of damping are obtained. The branching can, however, also take place in any other region of the connecting line.
It has proven particularly advantageous if at least one inner hose with a relatively small diameter which is oriented coaxially in the outer hose is provided in the elastic hose which is arranged as a line through which there is not a flow or as a parallel line. Said inner hose can be attached by one of its ends to the outer elastic hose. The connection of the outer and inner hoses can be made, for example, by means of a sleeve which is arranged between the outer and inner hoses, is connected to one end of the inner hose and is held by a sleeve-shaped clamp which is arranged around the outer hose. However, connection can also be made in any other way which is familiar to the person skilled in the art.
The free end of the inner hose which is not connected to the sleeve can be oriented in the direction of the pump or in the direction of the closed-off end of the elastic hose in the case of the line through which there is not a flow, or in the direction of the actuator in the case of the line which is guided in parallel. The sleeve can also be arranged in the center of the inner hose so that the latter has two free ends, one of which points in the direction of the pump, another in the opposite direction.
The additional combination of lines through which there is not a flow or guided in parallel, and an interruption in the fluid column in the line arrangement which is achieved by means of additional inner hoses can reduce the noise emissions considerably over wide rotational speed ranges of the pump.
A plurality of inner hoses can also be arranged in the outer elastic hose. These can all be pointing in the same direction or else in different directions. The length of the inner hoses can also vary. By means of the variants mentioned above, the degree of damping of the line arrangement according to the invention can be set precisely to the respective application cases.
It is also conceivable, in addition to the line through which there is not a flow or the line which is guided in parallel, to make part of the connecting line between the pump and the actuator from an elastic hose. In this hose it is also possible to provide inner hoses with relatively small diameters in the above-mentioned variations.
The invention will be explained in more detail below by reference to the exemplary embodiment illustrated in the drawings.